12. A runner at the start of a race generates 250 W of power as he accelerates to 5 m/s. If the runner has a mass of
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Answer:
<em>The kinetic energy of a spinning disk will be reduced to a tenth of its initial kinetic energy if its moment of inertia is made five times larger, but its angular speed is made five times smaller.</em>
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Explanation:
Let us first consider the initial characteristics of the angular motion of the disk
moment of inertia =
angular speed = ω
For the second case, we consider the characteristics to now be
moment of inertia = (five times larger)
angular speed = ω/5 (five times smaller)
Recall that the kinetic energy of a spinning body is given as
therefore,
for the first case, the K.E. is given as
and for the second case, the K.E. is given as
<em>this is one-tenth the kinetic energy before its spinning characteristics were changed.</em>
<em>This implies that the kinetic energy of the spinning disk will be reduced to a tenth of its initial kinetic energy if its moment of inertia is made five times larger, but its angular speed is made five times smaller.</em>